US confronts ‘Axis’: Who are Iran’s allies? Can they be deterred?

Since the Hamas-Israel war erupted Oct. 7, Iran-backed militias in Iraq and Syria have mounted more than 165 attacks against U.S. military bases in the region. After a cross-border drone strike killed three American soldiers in Jordan last week, the United States vowed to “hold accountable” those responsible.

American warplanes launched 85 strikes Friday against militias allied to Iran, and the U.S. promised more retaliation to come as it targets weapons depots, rocket stockpiles, and command-and-control infrastructure of Iran’s self-declared “Axis of Resistance.”

From Lebanon through Syria, and Iraq to Yemen, as well as in Gaza, the Iran-led “Axis” has been active in targeting Israel and its closest ally, the U.S. While the militias’ autonomy provides Iran with a degree of deniability, analysts say the current escalation is dangerously prone to overreach and miscalculation that could lead to a direct U.S.-Iran conflict.

American troops number 2,500 in Iraq and 900 in Syria, nominally to prevent a resurgence of the Islamic State (ISIS). But the uptick in militia attacks and the scale of U.S. counterstrikes – which sparked outrage among Iraqi officials – have effectively stalled U.S.-Iraqi talks underway prior to Oct. 7 that were progressing toward a long-term American withdrawal plan.

Who are Iran’s allies in Iraq?

When Islamic State fighters swept from Syria into Iraq and to the gates of Baghdad in June 2014, the U.S.-trained and equipped Iraqi military disintegrated. Yet Iran – which had supported Shiite militias in Iraq for years, as part of an insurgency against American occupation – immediately sent weapons and ammunition to Iraq, and helped marshal and support the newly formed, mostly Shiite Popular Mobilization Forces to fight back.

For years, U.S. airstrikes against ISIS were conducted in parallel with ground forces of the Iran-backed militias and reconstituted Iraqi armed forces. After ISIS was declared defeated in Iraq in late 2017, those Shiite militias – which have at times numbered more than 65 different groups – had sizable political clout and were officially brought under the wing of the Iraqi security forces.

Pro-Iran factions helped violently quell popular street protests that started in 2019, and since October 2023 have operated under the umbrella name of the Islamic Resistance of Iraq, which includes Kata’ib Hezbollah – one group long at the forefront of attacks on U.S. bases.

How much control does Iran have over its “Axis”?

“This is a set of armed groups that are closely aligned to Iran, and at times will take orders from Iran – but at other times will diverge; they do have some autonomy,” says Renad Mansour, head of the Iraq Initiative at the Chatham House think tank in London. “The word ‘proxy’ here is difficult, because it implies just working entirely on behalf of someone else. These groups have their own interests.”

Both Tehran and Washington have signaled repeatedly that they do not want a wider war that would put the two archfoes into direct conflict. Immediately after the three Americans were killed in Jordan, for example, Kata’ib Hezbollah claimed responsibility.

But then after direct intervention by Brig. Gen. Esmail Qaani, commander of Iran’s Qods Force, which handles the “Axis” across the region, and Iraqi Prime Minister Mohammed Shia al-Sudani, the militia issued a statement saying it would cease all attacks on Americans – and even indicated that it had been unhappily pressured by Iran.

“The logic of violence that Iran wants is to show force, but not to risk any escalation,” says Dr. Mansour.

Can the U.S. degrade the “Axis” from the air?

The record of achieving lasting militia degradation through airstrikes alone is not very promising, if the U.S. military experience in Afghanistan and Iraq is any measure.

U.S. Central Command says it struck seven different targets in Iraq and Syria. With the help of Britain and other regional partners, it has also been launching almost daily strikes against another Iran-backed group, the Houthis in Yemen, who have not been deterred from targeting Red Sea shipping.

One month ago, a U.S. drone strike in Baghdad killed a leader of the Harakat al-Nujaba militia, accused of planning attacks against American service members. Back in 2020, also in Baghdad, the U.S. assassinated Iran’s Maj. Gen. Qassim Soleimani, the Qods Force commander and architect of the “Axis of Resistance,” along with Abu Mahdi al-Muhandis, founder of Kata’ib Hezbollah and deputy leader of the Iraqi Shiite militia forces.

In addition to such targeted killings, for years, the U.S. has “struck [Iran-backed militias’] weapons depots and tried to financially strangle them through sanctions, and yet the groups have kept their capabilities and still operate across the region,” says Dr. Mansour.

“There can be intense military bombardment to go after adversaries, but that does not make a coherent strategy,” he says. “What’s becoming clear is the U.S., for all its military and economic might, fundamentally has a predicament: It does not have a sustainable approach for dealing with these groups.”

How are the U.S. strikes impacting Iraq?

While Washington aims to deter further attacks on U.S. forces, the stepped-up militia action linked to the Israel-Hamas war in Gaza and the new level of kinetic American response touch a raw nerve in Iraq.

“We already know the damage that the Americans can do – that’s the whole political sensitivity of this issue,” says Hamzeh Hadad, an Iraq expert and visiting fellow with the European Council on Foreign Relations. “So the Iraqis don’t need a reminder of what the Americans are capable of, which is why we always had that fear of, ‘Will this extend to that level?’”

And there is another practical concern, he says, about the continuing threat from the Islamic State. In Syria and Iraq, for example, the U.S. Department of Defense estimates that 1,000 dispersed ISIS fighters remain, and camps in Syria still hold tens of thousands of people linked to the original ISIS “caliphate.” Likewise, nearly 100 people were killed in Iran a month ago, in a double explosion claimed by the ISIS Khorasan branch.

“When this Iraqi militia decided to attack this American base bordering Iraq, Syria, and Jordan, you are arguably attacking a side that is keeping ISIS in check there,” says Mr. Hadad. “And the same can be said for the Americans: When they attack the bases on the border of Iraq and Syria, they are also attacking [militias] that are basically stationed on the border to take care of ISIS.”